I'm making a robot for a competition in which the robot have go thru a maze and pot three different coloured balls (balls already placed on the robot) in the respective coloured boxes..

i think two motors (for driving purpose) will do the job.. one for left, and other for right.. i'll be using two 12v batteries, one to power up the ics (obviously after stepping it down to 5v) and the other for the two motors..

one more thing.. i'm thinking of having a 4-wheeled robot.. 2 on each side.. and use a chain to drive both wheels with a single motor..

if we suppose that my robot weighs 5-6kg, what motors i should use? i need torque and a little speed too.. i need it to be quick to start and i also need it to stop instantly (obviously when signals are received from microcontroller).. please help!

if not chain, how do u suggest i drive both wheels with a single motor..?

You said you'd use two motors. I suggest driving the left rear wheel with one motor, and the right rear wheel with the other motor, and leaving the front wheels un-driven. If you can add servo-based steering, you'll be better at turning, but you can probably do without it.

Or just put in four motors. Motors are cheaper than transmissions and linkages these days... Look at, for example, the Wild Thumper series for design ideas.

if not chain, how do u suggest i drive both wheels with a single motor..?

You said you'd use two motors. I suggest driving the left rear wheel with one motor, and the right rear wheel with the other motor, and leaving the front wheels un-driven. If you can add servo-based steering, you'll be better at turning, but you can probably do without it.

Or just put in four motors. Motors are cheaper than transmissions and linkages these days... Look at, for example, the Wild Thumper series for design ideas.

if i let two front wheels undriven, i'll have issues it making 90 degree turns while standing.. :s can you suggest what exact motors should i use? a picture will help

2) Use two big wheels, and two smaller wheels that are just "limp" and ideally pivot. Casters, balls, cart wheels, whatever you want to call them. Turning the big wheels different directions will pivot the robot in place. With only two motors, this is the easiest to implement.

3) You probably want motors with built-in encoders, so you can tell whether one wheel is going faster than the other and compensate, to go straight.

4) You don't need the full weight * radius amount of torque, as long as you don't want to accelerate wildly (and can make soft start/stop part of your control.) Wheels turn very easily, at least if they are narrow and hard.

2) Use two big wheels, and two smaller wheels that are just "limp" and ideally pivot. Casters, balls, cart wheels, whatever you want to call them. Turning the big wheels different directions will pivot the robot in place. With only two motors, this is the easiest to implement.

3) You probably want motors with built-in encoders, so you can tell whether one wheel is going faster than the other and compensate, to go straight.

4) You don't need the full weight * radius amount of torque, as long as you don't want to accelerate wildly (and can make soft start/stop part of your control.) Wheels turn very easily, at least if they are narrow and hard.

You will need some motor controllers to drive them, too. And a microcontroller to tell the motor controllers what to do. Feel free to ask again if you don't know where to go from here!

thabk you so much! it really helped me out!-well i cant use more than 2 motors for driving purpose.. its in the rules..-casters.. i heard that the arena that they make is not perfectly levelled (friend's experience), so robots with casters had issues there, like stuck on small bumps.. thats why we dropped that idea..